1. Field of the Invention
The present invention relates to an accelerometer using an accelerometric sensor with flat pendular structure of the type described in U.S. Pat. No. 4,663,972.
2. Description of the Prior Art
It will be recalled that in the above patent this pendular structure is formed by micro-machining a substrate formed by a fine wafer of quartz (or other monocrystal) and by vacuum deposition of judiciously disposed conducting surfaces. It comprises a flat mobile mass (or test body) suspended from the rest of the structure by means of two thin parallel strips situated on each side of said mass.
These suspension strips have for thickness the thickness of the substrate and are extremely narrow. They allow the mobile mass to move in translation in a direction parallel to the plane of the substrate while opposing only a small resilient return force, so that the sensitive axis of the sensor is situated in the plane of the substrate.
These suspension strips carry conductors ensuring the electric continuity between metallized areas connected to the mobile mass and connection zones situated on the fixed part of the substrate.
Furthermore the above patent proposes, for servo-control of the sensor, a return motor using Laplace's force obtained by the action of a magnetic induction on a current flowing in at least one coil printed on one of the faces of the mobile mass.
It is clear that this solution, apart from the fact that it requires the formation of the coil, uses a magnetic circuit usually comprising a permanent magnet associated with pole pieces situated on one side of the mobile mass, in line with the coil, and a flux relooping plate disposed on the other side of said mass. In addition, it is necessary to provide delicate connections between the coil and the connection areas or the electronic circuits situated on the fixed part of the pendular structure, these connections being formed by conducting layers disposed on the suspension strips.
The aim of the invention is more particularly to provide an accelerometer comprising an accelerometric sensor of a type similar to the one described above, but using motorization and servo-control means of a type more appropriate for obtaining a simplified construction of the assembly, which is less space consuming and less costly, and which allows a very high degree of miniaturization.